Aspartame is a minor source of phenylalanine compared to the amounts you get from other foods, so this is not a cause for concern.

However, phenylalanine can reach toxic levels in people with a genetic disorder called phenylketonuria (PKU). Those who have PKU need to avoid foods high in phenylalanine, especially during childhood and adolescence (2).

Bottom Line: Aspartame is a source of phenylalanine, an essential amino acid. Phenylalanine has no harmful effects in healthy people, but it should be avoided by those with a genetic disorder called phenylketonuria (PKU).

The methanol produced during the digestion of aspartame is only a small part of the total dietary intake. For this reason, methanol from aspartame is not considered to be a health issue (7).

Bottom Line: As aspartame is digested, low amounts of methanol are formed. Aspartame is only a minor source of methanol in the diet, so it is not considered to be a problem.

Is Aspartame Bad For You?
Aspartame is highly controversial.

Thousands of websites claim that it is seriously harmful. Aspartame is blamed for hundreds of health problems, ranging from cancer to headaches.

However, most of these have not been confirmed by science (7, 8, 9).

Below is a review of the scientific evidence behind the most common claims.

Claim: Aspartame Causes Cancer
A few notable animal studies from the European Ramazzini Foundation suggest that aspartame may cause cancer (10, 11, 12).

However, other scientists have criticized these studies for using poor methods and not being very relevant to humans (7, 13).

One observational study in humans found a weak connection between certain types of cancer and aspartame, but only in men (14).

Other observational studies did not find an association between aspartame intake and brain or blood cancer (15, 16).

Additionally, scientific reviews have concluded that there is no evidence that aspartame in the human diet causes cancer (7, 17, 18).

Bottom Line: Several studies have researched the connection between aspartame consumption and cancer. Overall, there is no conclusive evidence to suggest that aspartame increases the risk of cancer in humans.

Claim: Aspartame Causes Weight Gain
As a low-calorie sweetener, aspartame is commonly consumed by people who want to enjoy the sweetness but need to limit their sugar intake.

Although it is clear that aspartame does not cause weight gain, its usefulness for weight loss has been questioned.

However, most studies suggest that replacing sugar with aspartame may be useful to prevent future weight gain (19, 20, 21).

Bottom Line: Consuming aspartame-sweetened foods and beverages is not an effective weight loss method. However, it may be useful to prevent future weight gain.

Claim: Aspartame Affects Mental Function
One scientific review speculated that aspartame could lead to various mental problems (22).

However, this review was heavily criticized for incorrect information, unsupported speculation and low-quality references (23).

In adults, studies have shown that aspartame has no effects on behavior, mood or mental function (24, 25, 26, 27, 28).

Studies in children have provided similar results (29, 30, 31, 32, 33).

Only one study has reported possible adverse effects from aspartame consumption. Patients with depression reported more severe symptoms when they were given capsules with aspartame (34).

Bottom Line: Aspartame appears to have no adverse effects on behavior, mood or mental performance. One study indicates adverse effects in patients with depression, but the evidence is weak.

Claim: Aspartame Causes Seizures
A few small studies have investigated the effects of aspartame on seizures. Most of them found no link (35, 36).

One small study in children with absence seizures concluded that aspartame increased brain activity linked to seizures (37).

Bottom Line: There is no conclusive evidence that aspartame causes seizures. One study indicated an increased risk for absence seizures in children.

Claim: Aspartame Causes Headaches
Several studies have investigated the effects of aspartame on headaches.

Most of them have found no link (8, 25, 38).

One study showed that aspartame significantly increased how often people got headaches, but not how long the headaches lasted or how severe they were.

However, there was high variability between individuals, which makes the results unreliable (39).

Another study found a weak link between aspartame and the frequency of headaches. No difference in the severity or duration of headaches was reported (40).

Bottom Line: There is limited evidence that aspartame can increase the frequency of headaches. More studies are needed.

Take Home Message
Aspartame is one of the world’s most studied food additives, and the majority of studies conclude that it is safe.

Almost every study found no adverse effects from consuming it. Some of these studies included people who actually considered themselves to be sensitive to aspartame (41).

All things considered, there is no good evidence to claim that aspartame is harmful.

However, it is impossible to rule out some rare cases of real aspartame sensitivity or allergy.

If you feel like you have an adverse reaction to aspartame, then simply avoid it.

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2 Comments

American Beverage Association, ABA CommunicationsNovember 24, 2015

As noted here, aspartame is a safe ingredient, as repeatedly verified by science. Most recently, the European Food Safety Authority determined aspartame is safe for consumption by the general population, and that this ingredient does not cause cancer, or other alleged health issues. These findings add to decades of scientific research reinforcing the safety of this ingredient, as well as the positions of regulatory agencies around the globe, including FDA. Bottom line: consumers can enjoy products that contain aspartame knowing they are safe and also effective as a diet tool: http://bit.ly/Ik4zjC.

Great job breaking down aspartame and addressing some of the myths and misconceptions about it’s safety.

As mentioned in this article, aspartame is broken down into three simple building blocks that are commonly found in many other foods. After consumption, aspartame is quickly broken down and never enters circulation whole. These building blocks are consumed in very minute amounts and undergo their regular metabolism. As a result, it is highly unlikely that aspartame could cause the health effects that some might claim.

Diet products are useful tools for weigh and disease management for those with dietary restrictions, such as diabetes. These products are helpful because they provide a sweet taste with little or no calories. As mentioned, there is no reason to believe that these products would lead to weight gain. On the contrary, studies have shown that they can be helpful in weight loss and management.